Testing for the Presence of Water

Want to know a secret? Young chemists may dismiss the idea of needing to test for the presence of water after a chemical reaction,  but when you tell them they can create invisible ink in the process, that might get their attention! The third part in a series of ten short videos discusses two simple tests that can indicate water has formed by hydrating anhydrous solids.

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Instructional Ideas
  • Provide an article about the uses of invisible ink throughout history; follow up by having students make their own cobalt (II) chloride solution and try their hand at secret messages
  • Ask the class to show the differences between an anhydrous substance and one that is hydrated by looking at their chemical formulas
Classroom Considerations
  • Turn subtitles on to assist with note-taking
Pros
  • Video includes the interesting, real-world application of cobalt (II) chloride as invisible ink and as an indicator of water's presence
  • Can be used as a stand-alone resource or shown as a continuation of the second video in the series, which also shows chemical tests
Cons
  • None